US blood supplies are becoming increasingly infected with Babesia, a tickborne parasite of red blood cells. The infection is transmitted through blood transfusions. Since 1979, when transfusion-associated babesiosis was first reported, the number of reported cases has been progressively increasing, the CDC (Centers for Disease Control and Prevention) announced in Annals of Internal Medicine after carrying out a collaborative study of the last thirty years.

The authors comment on 159 reported cases of Babesia-tainted blood used in transfusions that led to babesiosis from 1970 through 2009 – 77% of them occurred after 2000.

Many individuals infected with Babesia may feel fine; they have no symptoms. However, they can pass the infection on if they donate blood.

There is no FDA-approved screening test for prospective blood donors that detects Babesia, the authors wrote.

Babesiosis is a parasitic disease, very similar to malaria, and is caused by Babesia, a protozoan parasite of the blood. Babesia are believed to be the second most common blood parasites of mammals, after trypanosomes. Although much less common in humans than other mammals, experts say reported human cases have risen over the last decade mainly because of better medical awareness.

Babesiosis is a potentially life-threatening complication of blood transfusion. However, it is treatable. An infected individual has a risk of multi-organ failure, and even death. Patients without a spleen, individuals with weakened immune systems, and the elderly are more vulnerable to complications.

The authors write that there is an urgent need for a screening test and prevention strategies. A number of medical device and diagnostic companies are working on developing tests for Babesia for donor-screening purposes.

Lead author, Barbara Herwaldt, M.D., M.P.H., CDC medical epidemiologist, said:

“We want clinicians to become more aware of babesiosis, including the small possibility of transmission via blood transfusion. If a patient develops unexplained fever or hemolytic anemia after a transfusion, babesiosis should be considered as a possible cause, regardless of the season or U.S. region.”

Babesiosis is most commonly spread by tick bites. The tick is tiny, about the size of a poppy seed. Babesiosis is also human-transmissible via blood transfusions if the donor blood is contaminated.

Taking measures to safeguard blood supply and avoid being bitten by the ticks would make a significant difference to the babesiosis rate in the USA.

The majority of babesiosis cases that originated from ticks have occurred during the warm months in Wisconsin, Rhode Island, New York, New Jersey, Minnesota, Massachusetts, and Connecticut.

Nineteen US states have reported cases of infection through transfusion, which can occur at any time of year.

Even severe cases of babesiosis are easily overlooked, unless the doctor decides to carry out a target diagnosis, Herwaldt explained. Babesiosis is commonly mistaken for malaria, another parasitic infection that affects red blood cells.

Babesiosis became a notifiable diseases throughout the USA in January of this year.

The CDC says that authorities need accurate data on tickborne and transfusion-transmitted babesiosis cases in order to ensure the quality of donor blood supplies.

Humans most commonly become infected with one of two species of BabesiaB. microti or B. divergens

Babesiosis complications may include congestive heart failure, renal failure and respiratory failure. It can be fatal in about 5% to 10% of hospitalized patients, and is especially dangerous for the elderly, those co-infected with Lyme disease, and people who have no spleen. Some patients infected with B divergens may develop jaundice, a high persistent fever, chills and sweats. B. divergens has a much higher fatality rate than B. microti.

Signs and symptoms of babesiosis generally appear between 1 to 8 weeks after the person becomes infected.

Written by Christian Nordqvist